• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1219-1220
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• 2012

• Nuclear Engineering and Technology
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• 제14권2호
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• pp.51-63
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• 1982

한국에너지연구소에서 개발한 1차원적 제논과도현상해석 코드 DD1D를 사용하여 가압경수로심의 축방향 제논진동에 대한 안정성을 조사하였다. 노심의 출력준위, 감속재온도계수, 노심 입구온도, 도플러출력 계수 그리고 연소도의 변화가 노심의 축방향 안정성에 미치는 효과를 조사하기 위하여 고리1호기의 설계 및 운전자료를 이용하였으며 본 민감도 분석을 통하여 고리 1호기의 노심은 주기 초에는 축방향 제논진동에 대하여 안정하나 연소도가 증가함에 따라 안정도가 차츰 감소하여 주기 말에는 불안정해진다는 것을 알았다. 이같이 연소도가 증가함에 따라 노심의 안정도가 감소하는 이유는 연소도 변화에 따라 축방향의 출력분포, 감속재온도 계수 및 도플러출력계수가 변하기 때문이다. 본 연구를 통하여 출력밀도가 높은 대형 가압 경수로의 경우 전 주기동안 축방향제논진동에 대하여 안정된 노심을 설계하기 힘들다는 결론에 도달하였다.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.61-72
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• 2012

The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

• 대한기계학회논문집B
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• 제24권6호
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• pp.834-844
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• 2000

In this study, an off-design performance analysis procedure is developed based on Two-zone model and TEIS model. In Two-zone model, there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller is calculated by using TEIS model which regards the impeller as two successive rotating elements in series. At impeller exit, the mixing process occurs with an increase in entropy, that is to say, a decrease in total pressure. In loss models including Two-zone and TEIS model, some empirical parameters have a great influence on overall performance curve. So these parameters' influences on the overall performance curve are investigated and compared with experimental data.

• Steel and Composite Structures
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• 제33권1호
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• pp.93-109
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• 2019

In the present study, vibration analysis of double bonded micro sandwich cylindrical shells with saturated porous core and carbon/boron nitride nanotubes (CNT/BNNT) reinforced composite face sheets under multi-physical loadings based on Cooper-Naghdi theory is investigated. The material properties of the micro structure are assumed to be temperature dependent, and each of the micro-tubes is placed on the Pasternak elastic foundations, and mechanical, moisture, thermal, electrical, and magnetic forces are effective on the structural behavior. The distributions of porous materials in three distributions such as non-linear non-symmetric, nonlinear-symmetric, and uniform are considered. The relationship including electro-magneto-hydro-thermo-mechanical loadings based on modified couple stress theory is obtained and moreover the governing equations of motion using the energy method and the Hamilton's principle are derived. Also, Navier's type solution is also used to solve the governing equations of motion. The effects of various parameters such as material length scale parameter, temperature change, various distributions of nanotube, volume fraction of nanotubes, porosity and Skempton coefficients, and geometric parameters on the natural frequency of double bonded micro sandwich cylindrical shells are investigated. Increasing the porosity and the Skempton coefficients of the core in micro sandwich cylindrical shell lead to increase the natural frequency of the structure. Cylindrical shells and porous materials in the industry of filters and separators, heat exchangers and coolers are widely used and are generally accepted today.

• Computers and Concrete
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• 제24권3호
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• pp.185-192
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• 2019

In this paper, the buckling of micro sandwich hollow circular plate is investigated with the consideration of the porous core and piezoelectric layer reinforced by functionally graded (FG)carbon nano-tube. For modeling the displacement field of sandwich hollow circular plate, the high-order shear deformation theory (HSDT) of plate and modified couple stress theory (MCST) are used. The governing differential equations of the system can be derived using the principle of minimum potential energy and Maxwell's equation that for solving these equations, the Ritz method is employed. The results of this research indicate the influence of various parameters such as porous coefficients, small length scale parameter, distribution of carbon nano-tube in piezoelectric layers and temperature on critical buckling load. The purpose of this research is to show the effect of physical parameters on the critical buckling load of micro sandwich plate and then optimize these parameters to design structures with the best efficiency. The results of this research can be used for optimization of micro-structures and manufacturing different structure in aircraft and aerospace.

• 한국추진공학회지
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• 제27권1호
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• pp.27-36
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• 2023

소형로켓엔진에 적용되는 기체-액체 스월 동축형 인젝터의 분무성능을 파악하고자 형상변수와 추진제의 공급조건을 변화시켜 수류시험을 수행하였다. 인젝터의 형상변수인 스월 챔버의 직경 및 수축부의 각이 증가할수록 스월 강도가 증대되어 분무성능이 향상되었다. 또한, 기체-액체의 운동량 플럭스 비가 증가함에 따라 기체 유동이 액적 일부를 분무액막에서 이탈시켜, 분무시트의 중심부에서 gas-droplet mixture core가 형성되었다.

• 한국진공학회지
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• 제6권3호
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• pp.287-292
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• 1997

본 실험은 고밀도 플라즈마원인 inductively coupled plasma(ICP)를 이용하여 실리카 도파로의 코아를 형성하고자 하였다. $CF_4/CHF_3$유량비, bias power 및 source power 등의 변화에 따른 산화막의 식각 특성 즉 식각 속도, 식각 단면 및 식각된 표면의 거칠기 등의 변화를 검토하였다. 또한 single Langmuir probe 및 optical emission spectroscopy(OES)를 이용하여, 식각 변수에 따른 ICP의 플라즈마 특성을 관찰하였다. 이상의 결과를 토대로, $SiO_2-P_2O_5$로 구성된 실리카 도파로의 코아(core)층을 형성하였고, 이때 최적화된 식각 조건 에서 식각 속도는 380nm/min이고, 마스크 층으로 사용된 Al(Si 1%)와 산화막과의 식각 선 택비는 30:1이상이였다. 형성된 실리카 도파로를 scanning electron microscopy(SEM)으로 관찰한 결과, 코아층의 식각 단면이 수직하고 패턴 선폭의 손실이 거의 없음을 확인하였다.

• Nuclear Engineering and Technology
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• 제35권4호
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• pp.356-368
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• 2003

Material properties such as coolant specific heat, film heat transfer coefficient, cladding thermal conductivity, surface diffusion coefficient of the multi-bubble are improved in MACSIS-Mod1. The axial power and flux profile module was also incorporated with irradiation history. The performance and feasibility of the updated driver fuel pin have been analyzed for nominal parameters based on the conceptual design for the KALIMER breakeven core by MACSIS-MOD1 code. The fuel slug centerline temperature takes the maximum at 700mm from the bottom of the slug in spite of the nearly symmetric axial power distribution. The cladding mid-wall and coolant temperatures take the maximum at the top of the pin. Temperature of the fuel slug surface over the entire irradiation life is much lower than the fuel-clad eutectic reaction temperature. The fission gas release of the driver fuel pin at the end of life is predicted to be $68.61\%$ and plenum pressure is too low to cause cladding yielding. The probability that the fuel pin would fail is estimated to be much less than that allowed in the design criteria. The maximum radial deformation of the fuel pin is $1.93\%$, satisfying the preliminary design criterion ($3\%$) for fuel pin deformation. Therefore the conceptual design parameters of the driver fuel pin for the KALIMER breakeven core are expected to satisfy the preliminary criteria on temperature, fluence limit, deformation limit etc.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1584-1602
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• 2024

It is vital to output the required electrical power following various task requirements when the space reactor power supply is operating in orbit. The dynamic performance of the closed Brayton cycle thermoelectric conversion system is initially studied and analyzed. Based on this, a load tracking power regulation method is developed for the liquid metal cooled space reactor power system, which takes into account the inlet temperature of the lithium on the hot side of the intermediate heat exchanger, the filling quantity of helium and xenon, and the input amount of the heat pipe radiator module. After comparing several methods, a power regulation method with fast response speed and strong system stability is obtained. Under various changes in power output, the dynamic response characteristics of the ultra-small liquid metal lithium-cooled space reactor concept scheme are analyzed. The transient operation process of 70 % load power shows that core power variation is within 30 % and core coolant temperature can operate at the set safety temperature. The second loop's helium-xenon working fluid has a 65K temperature change range and a 25 % filling quantity. The lithium at the radiator loop outlet changes by less than ±7 K, and the system's main key parameters change as expected, indicating safety. The core system uses less power during 30 % load power transient operation. According to the response characteristics of various system parameters, under low power operation conditions, the lithium working fluid temperature of the radiator circuit and the high-temperature heat pipe operation temperature are limiting conditions for low-power operation, and multiple system parameters must be coordinated to ensure that the radiator system does not condense the lithium working fluid and the heat pipe.